An update to the event that will be unfolding today. For us, most of the severe will come after midnight tonight, so please be sure to have a weather radio handy, as night time is always the worst time for weather like this. The darkness makes it almost impossible to spot tornadoes, and the type of tornadoes that spin with systems like these are quick and not often seen on a radar. For most of north and northeast Georgia, wind damage will be the biggest threat. Screaming winds just above the surface can mix down in any thunderstorm and bring high winds to ground level, and one way quick spin up tornadoes develop.

...SUMMARY... SEVERE THUNDERSTORMS CAPABLE OF DAMAGING WINDS AND TORNADOES WILL BE LIKELY OVER PORTIONS OF THE GULF COAST STATES TUESDAY. A FEW OF THE TORNADOES MAY BE STRONG...ESPECIALLY TUESDAY AFTERNOON AND INTO TUESDAY NIGHT.

...SYNOPSIS... STRONG SHORTWAVE TROUGH WILL PROGRESS ACROSS THE SRN PLAINS AND LWR MS VALLEY DURING THE PERIOD WHILE RAPIDLY DEEPENING. THE INITIALLY OPEN WAVE IS EXPECTED TO DEVELOP A CLOSED CIRCULATION BY TUESDAY EVENING AS IT MATURES. STRONG SLY/SWLY LOW-LEVEL FLOW WILL DEVELOP AHEAD OF THE SYSTEM ACROSS THE LWR MS VALLEY AND SOUTHEAST WHILE A STRONG MID-LEVEL JET PIVOTS AROUND THE UPPER LOW. THE RESULTING KINEMATIC ENVIRONMENT WILL BE VERY FAVORABLE FOR SEVERE TSTMS...PRIMARILY ACROSS THE LWR MS VALLEY AND PORTIONS OF THE SOUTHEAST.

...UPPER TX COAST EWD THROUGH MUCH OF THE SOUTHEAST...SURFACE LOW INITIALLY CENTERED OVER THE TX HILL COUNTRY IS EXPECTED TO RAPIDLY DEEPEN AS IT TRACKS NEWD ACROSS NRN LA AND MS. AS MENTIONED IN THE SYNOPSIS... STRONG LOW-LEVEL FLOW IS EXPECTED AHEAD OF THE LOW... WHICH WILL ENCOURAGE MOISTURE RETURN ACROSS THE LWR MS VALLEY AND GULF COAST. THE CHARACTER OF THIS MOISTURE RETURN IS THE PRIMARY UNCERTAINTY REGARDING THE EXTENT OF THE SVR THREAT ACROSS THE REGION. GUIDANCE IS IN RELATIVELY GOOD AGREEMENT THAT DEWPOINTS WILL STRUGGLE TO REACH THE MID 60S... WHICH WHEN COMBINED WITH POOR LAPSE RATES RESULTS IN RATHER MEAGER INSTABILITY. WARM SECTOR IS CURRENTLY EXPECTED TO BE CHARACTERIZED BY DEWPOINTS AROUND 61-64 DEG F AND MLCAPE LESS THAN 700 J PER KG.

DESPITE LIMITED INSTABILITY... THE KINEMATIC FIELDS WILL BE VERY FAVORABLE FOR SVR TSTMS. AS THE MID-LEVEL JET /80-100 KT AT 500 MB/ PIVOTS AROUND THE UPPER LOW IT WILL EJECT OUT OVER THE WARM SECTOR AND ITS ASSOCIATED STRONG LOW-LEVEL FLOW... RESULTING IN A SYNOPTICALLY FAVORABLE SET-UP FOR DISCRETE TSTMS. 0-6 KM BULK SHEAR WILL LIKELY BE AROUND 50-60 KT. SOME GUIDANCE HAS 0-1 KM SRH VALUES OVER 400 M2/S2 AND 0-3 KM SRH VALUES OVER 600 M2/S2. ANY PRE-FRONTAL... WARM SECTOR CONVECTION WILL LIKELY BE SUPERCELLUAR AND CAPABLE OF PRODUCING ALL SEVERE HAZARDS... INCLUDING TORNADOES. A MORE DISCRETE MODE MAY ALSO BE REALIZED WITH ANY ACTIVITY THAT DEVELOPS ALONG THE FRONT DURING THE EVENING WHEN THE STRONGEST PORTION OF THE MID-LEVEL JET MOVES INTO THE REGION...WITH THE RESULTING FAST STORM MOTION TAKING STORMS INTO THE WARM SECTOR. BOWING LINE SEGMENTS ARE ALSO PROBABLE WITH AN INCREASED DAMAGING WIND POTENTIAL.

​ HIGHEST CONFIDENCE IN TORNADOES CURRENTLY EXISTS FROM PORTIONS OF SRN LA NEWD INTO SRN AL WITH THE BULK OF THIS THREAT OCCURRING AFTER 00Z. GIVEN THE STRENGTH OF THE LOW-LEVEL FLOW...SOME POTENTIALLY SIGNIFICANT TORNADOES ARE POSSIBLE.

And this from the Atlanta NWS office...

SHORT TERM /TODAY THROUGH WEDNESDAY/...MAIN CONCERN IN THE SHORT TERM CONTINUES TO BE THE POTENTIAL FOR STRONG TO SEVERE STORMS TONIGHT AND EARLY ON WEDNESDAY... ALONG WITH POSSIBLE FLOODING FROM LOCALLY HEAVY RAIN.

ALTHOUGH A LULL IN THE CONVECTIVE ACTIVITY MAY OCCUR TODAY AS OUR NEXT STORM SYSTEM DEEPENS OVER TEXAS... DON`T LET THIS LOWER YOUR GUARD AS COMPUTER MODELS CONTINUE TO SHOW GOOD AGREEMENT WITH THIS STRONG STORM SYSTEM LIFTING EASTWARD THIS EVENING AND TRACKING ACROSS THE TENNESSEE VALLEY ON WEDNESDAY. THIS WILL DRAG A STRONG COLD FRONT ACROSS THE AREA EARLY ON WEDNESDAY WITH WIDESPREAD SHOWERS AND THUNDERSTORMS DEVELOPING ALONG AND WELL OUT AHEAD OF THE APPROACHING COLD FRONT.

AT THIS TIME IT APPEARS A SIGNIFICANT SEVERE WEATHER EVENT IS UNFOLDING AS STRONG 40-50KT 0-1KM BULK SHEAR AND 400-600 J/KG MUCAPE SHOULD BE SUFFICIENT TO SUPPORT THE DEVELOPMENT OF SUPERCELL STORMS... WITH DAMAGING WINDS AND ISOLATED TORNADOES BEING THE MAIN THREATS... ALTHOUGH SMALL HAIL CANNOT BE RULED OUT WITH THE STRONGER STORMS. AT THIS TIME IT APPEARS THE INITIAL THREAT WILL COME FROM DISCRETE SUPERCELLS THAT DEVELOP AHEAD OF A SQUALL LINE... AND PUSH INTO NW AND WEST CENTRAL GA SOMETIME BETWEEN LATE THIS EVENING OR SHORTLY AFTER MIDNIGHT TONIGHT.

​THESE STORMS WILL CONTINUE TO PUSH EASTWARD OVERNIGHT AND WILL BE FOLLOWED BY A DISTINCT SQUALL LINE THAT APPEARS TO PUSH ACROSS THE AREA SOMETIME BETWEEN 3 AM AND 11 AM WEDNESDAY MORNING. THIS QLCS TYPE SQUALL LINE WILL LIKELY BE THE MAIN SEVERE WEATHER PRODUCER... BRINGING A GREATER POTENTIAL FOR MORE WIDESPREAD DAMAGING WINDS... ALONG WITH A FEW EMBEDDED TORNADOES.

THIS SECOND WAVE OF CONVECTION WILL WARRANT MUCH CONCERN AS THE STRONG UPPER LOW OVER TX KICKS EAST AND INTERACTS WITH INCREASING AREA OF INSTABILITY AND DEEP LAYER SHEAR TO SUPPORT STRONG TO POSSIBLY SEVERE STORM DEVELOPMENT. THIS HAS PROMPTED SPC TO PLACE MUCH OF THE FORECAST AREA IN A MARGINAL RISK FOR SEVERE STORMS AND A SLIGHT RISK AREA ALONG AND WEST OF A CARROLLTON TO THOMASTON TO AMERICUS LINE. AT THIS TIME... THIS THREAT APPEARS TO BE GREATEST FROM LATE TUESDAY EVENING THROUGH WEDNESDAY MORNING... BUT STAY TUNED AS THIS COULD CHANGE.

AN INTENSE MID-LEVEL SHORTWAVE TROUGH WILL TRACK EASTWARD FROM TX ACROSS THE GULF COAST REGION ON TUESDAY. A 100+ KT MIDLEVEL JET STREAK WILL OVERSPREAD THE NORTHERN GULF COAST AND PIVOT NORTHEAST INTO CENTRAL AL/WESTERN GA BY WEDNESDAY MORNING.

AT THE SURFACE... LOW PRESSURE OVER EAST TX/WESTERN LA WILL LIFT NORTHEAST ACROSS THE LOWER MS VALLEY WHILE RAPIDLY INTENSIFYING. A TRAILING COLD FRONT WILL MOVE ACROSS EAST TX INTO WESTERN LA BY LATE AFTERNOON AND ACROSS MS/AL OVERNIGHT. LOW TO MID 60S DEWPOINTS ARE ALREADY IN PLACE ALONG THE UPPER TX AND NORTHERN GULF COASTS.

THIS MOISTURE WILL CREEP NORTHWARD INTO CENTRAL MS/AL/GA BY TUESDAY AFTERNOON... WITH DEWPOINTS FURTHER NORTH ACROSS NORTHERN MS/AL/GA FROM THE MID TO UPPER 50S. SOME DAYTIME CLOUDINESS AND SHOWERS AND THUNDERSTORMS ACROSS THE WARM SECTOR IN MS/AL/GA WILL LIMIT DESTABILIZATION... BUT STEEPENING MIDLEVEL LAPSE RATES SHOULD ALLOW FOR MUCAPE VALUES APPROACHING 500-1000 J/KG.

IMPRESSIVE VERTICALLY VEERING DEEP LAYER WIND PROFILES AND A STRONG SOUTHWESTERLY LOW LEVEL JET OF 60+ KT WILL FAVOR SUPERCELLS WITH SOME BOWING LINE SEGMENTS. DAMAGING WINDS AND TORNADOES... PERHAPS ONE OR TWO STRONG TORNADOES... WILL BE POSSIBLE.

​EXPECT THE GREATEST THREAT FROM PARTS OF SOUTHERN LA INTO SOUTHERN MS DURING THE AFTERNOON AND CONTINUING ACROSS SOUTHERN AL AND THE WESTERN FL PANHANDLE THROUGH THE OVERNIGHT HOURS. ADDITIONALLY... SEVERE HAIL APPEARS POSSIBLE WITH COOLING MID-LEVEL TEMPERATURES RESULTING IN 700-500 MB LAPSE RATES NEAR 7 DEG C/KM. SOME UNCERTAINTY WITH REGARDS TO THE EASTERN EXTENT OF THE SLIGHT AND ENHANCED RISK AREAS CONTINUES... AND THESE AREAS MAY NEED TO BE RE-EVALUATED IN COMING OUTLOOKS.

As you can see from the images below, it appears that we will eventually fall into the Slight Risk category and i wouldn't be surprised to see our area elevated to Enhanced possibly later today. Also, VERY heavy rain coming in over the next three days, with almost 3-4" expected over a large area of north Georgia.

0-1 km Bulk Shear

Storm Relative Helicity

0-6 km Bulk Shear

Storm Motion Speed in Knots

500 mb Vorticity

Surface Based CAPE - While not very strong, still enough CAPE to interact with very high shear for severe potential.

Luckily it will be coming through in the early morning hours... it it were afternoon with some daytime heating, this might be a bad day for a lot of people.

The GFS/NAM are still showing a high shear/low CAPE event. I want to update you with some severe parameter maps for 7 AM Tuesday morning, and what those mean in terms of severe weather. More on this later.

Storm Motion Speed - This maps shows the speed in knots and the direction of the storm motion.

0-6 km Bulk Shear - The Boundary Layer through 6-km above ground level shear vector denotes the change in wind throughout this height. Thunderstorms tend to become more organized and persistent as vertical shear increases. Supercells are commonly associated with vertical shear values of 35-40 knots and greater through this depth.

Significant Tornado Parameter - Right now 1 or less. A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the "effective layer" version of STP.

0-1 km Storm Relative Helicity - SRH (Storm Relative Helicity) is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and is calculated for the lowest 1-km and 3-km layers above ground level. There is no clear threshold value for SRH when forecasting supercells, since the formation of supercells appears to be related more strongly to the deeper layer vertical shear. Larger values of 0-3-km SRH (greater than 250 m**2/s**2) and 0-1-km SRH (greater than 100 m**2/s**2), however, do suggest an increased threat of tornadoes with supercells. For SRH, larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.

Surface Based CAPE - A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the "effective layer" version of STP.